Hi Nigel
The inlet is under the sink, aft (to the left in the picture). A new sea-cock was fitted in the undersink locker and the sink outlet pipe moved to the new sea-cock. The inlet for the toilet was then attached to the existing sea-cock (the only reason for swapping these around was to achieve a better lead for the new hoses).
When pumping out, all the exit water feeds through the holding tank. This can be keep in the tank by means of a shut off valve at the sea-cock, or can flow straight through the tank and out if appropriate.
The outlet is gravity fed, you can see on the picture the holding tank is slightly raised on wooden blocks to allow for enough of a drop. The outlet is fitted next to the log, the depth sounder had to be moved a few inches to allow room.
I have some additional pictures that may help, but am having difficulty attaching them here. My email address is in the members' handbook so please feel free to email me if you would me to send them to you.
Regards
Andy